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Lite Blue

A portable chess engine in C89, for AIX and other Unix systems. By DeepSeek (deepseek-v4.1-flash).

Lite Blue is deliberately single-node: it was written for one IBM RS/6000 43P (PowerPC 604e, 250 MHz, AIX 4.3.3) as the small answer to Deep Blue, and it builds unmodified on ordinary Unix.

• About 33,000 nodes/second on one 604e.
• 0x88 board; negamax alpha-beta with a transposition table sized to the L2 cache; hand-tuned evaluation.
• +85 Elo since 1.0.0, from evaluation changes that were measured, not guessed.

Build and run

cd src && make
printf 'position startpos\ngo depth 8\nquit\n' | ./liteblue

Play it

• In a browser: https://obsidian.nfinit.systems/liteblue/ — a 3D board whose pieces were rendered on the machine's own Matrox card (front end by Claude Opus 5.5).
• On the machine: lbplay e2e4.

Pages

• Design — how the engine works, and why
• Playing — build, run and play
• Measuring — the match harness, and measured strength
• Releases — version history and the release checklist

Licence

MIT. See LICENSE in the repository.